The present invention relates to a biosignal display apparatus for detecting a biosignal such as a pulse wave and displaying a detection result.
FIG. 3 is a functional block diagram showing the operation of a conventional biosignal display apparatus. A biosignal detecting means 300 detects and amplifies a biosignal such as a pulse wave. A signal converting means 301 performs, at predetermined intervals, analog-to-digital conversion on the biosignal as amplified by the biosignal detecting means 300. A calculation means 302 stores the biosignal as converted by the signal converting means 301, and performs a fast Fourier transform upon storage of 2.sup.n data. A display the means 303 displays calculation results of the calculation means 302.
The above type of biosignal display apparatus is disclosed in Japanese Unexamined Patent Publication No. Hei. 1-27534, for instance.
It is generally known to subject a biosignal such as a pulse wave to a fast Fourier transform in analyzing it in the frequency domain. Low-frequency components make up a large part of a biosignal detected from a living body. For example, if frequency-domain analysis is conducted to perform calculation on the interval of a pulse wave, a spectrum will range from 0.5 to 4 Hz. It takes 16 seconds to acquire, for instance, 128 data values that are necessary for frequency-domain analysis by performing analog-to-digital conversion at intervals corresponding to 8 Hz according to the sampling theorem. A calculation resolution of about 3.75 pulses per minute is obtained by performing a general fast Fourier transform under the above condition.
As described above, it takes an excessive time to perform a frequency-domain calculation, with high accuracy, on a biosignal such as a pulse wave using a frequency-domain analyzing technique, and the display of calculation results is delayed. As a result such an apparatus is not convenient to use.